Lawson Inc. said Wednesday one of its outlets in Sapporo lost 106 blank sheets used to make tickets for concerts and plays.
The nation's second-largest convenience store operator discovered the sheets were missing when 35 counterfeit tickets, made on the missing sheets, were used last month at a musical in Tokyo, company officials said.
Lawson officials said up to four tickets can be printed on each sheet.
The company's operating manual calls for each store to check the number of such blank sheets each day. The rule was not observed at the Sapporo outlet.
Lawson has informed the Hokkaido Prefectural Police of the missing sheets and has launched its own investigation into the incident.
The sheets are used to print tickets in-store. They can be booked on the Internet and by other means.
The missing sheets had been kept in a place that could be reached from the store counter, Lawson officials said.